Question

No light passes through two perfect polarizing filters with perpendicular axes. However, if a third polarizing filter is placed between the original two, some light can pass. Why is this? Under what circumstances does most of the light pass?

a. The third filter acts as a quarter-wave plate, altering polarization.
b. The third filter absorbs unwanted wavelengths.
c. The third filter allows multiple paths for polarization.
d. The third filter reduces intensity and allows more selective transmission.

Answer 1

A third polarizing filter allows multiple paths for polarization, so some light can pass through two perfect polarizing filters with perpendicular axes.

Step-by-step explanation:

The reason that some light can pass through two perfect polarizing filters with perpendicular axes when a third polarizing filter is placed between them is because the third filter allows multiple paths for polarization.

When the axes of the first and second filters are aligned (parallel), all of the polarized light passed by the first filter is also passed by the second filter. But when the axes are perpendicular, no light is passed by the second filter.

In the case where a third filter is placed between the original two, the third filter can allow some light to pass if its axis is at an angle between the first and second filters' axes.